Beading the maxillary cast creates a defined border on the cast, which guides the fabrication of the wax rim or custom tray. This border helps achieve intimate tissue contact during impression making, ensuring a precise seal along the denture's periphery. Proper beading prevents overextension or underextension of the tray, which is critical for capturing accurate functional anatomy and improving denture stability. Thus, beading is essential for molding the impression material to closely adapt to the mucosa, enhancing overall fit and comfort.

Reference: Complete Denture Prosthodontics, Zarb & Bolender, 12th Edition.